ProfilesDirectory
The ProfilesDirectory setting specifies the path to the user profile folder. Use this setting to move the user profile folder (typically %SYSTEMDRIVE%Users) to another location during Setup or Sysprep. The destination path can be on a volume other than the system drive, as long as it meets the following requirements:
- It must be on an NTFS volume.
- It must not be the path of another operating system user profile folder.
- It must not contain any serviceable components.
- This setting can be used to keep system data separate from user data. If Windows is re-installed on the system volume, a user with administrative rights can manually recover data from this location.
Important:
These settings should be used only in a test environment. By changing the default location of the user profile directories or program data folders to a volume other than the System volume, you will not be able to service your Windows installation. Any updates, fixes, or service packs will fail to be applied to the installation. Microsoft does not recommend that you change the location of the user profile directories or program data folders.
Caution:
Using ProfilesDirectory to redirect folders to a drive other than the system volume blocks upgrades. Using ProfilesDirectory to point to a directory that is not the system volume will block SKU upgrades and upgrades to future versions of Windows. For example if you use Windows Vista Home Premium with ProfilesDirectory set to D:, you will not be able to upgrade to Windows Vista Ultimate or to the next version of Windows. The servicing stack does not handle cross-volume transactions, and it blocks upgrades.
Reference: http://support.microsoft.com/kb/949977
